Layering

Purpose - To observe layering of undissolved materials.

Materials2 tablespoons(30 ml) of any large dried bean

2tablespoons (30 ml) flour quart (liter) glass jar with a lid tap water

Procedure

■ Place the beans and flour in the jar.

■ Fill the jar with water.

■ Screw the lid on tightly.

■ Shake the jar to mix all the materialsthoroughly.

■ Let the jar stand undisturbed for 20 minutes.

■ Observe.

Results The beans settle first with a fine layer offlour on top.

Why? The beans andflour are not capable of being dissolved in the water. As soon as the shakingstops, gravitystarts pullingthese undissolved Materials - down. The heavier beans settle first. The tinyflour particles remain suspended in the water for a few minutes, but finallyare pulled to the bottom of the jar.

Amixture containing particles suspended in a liquid that usually settles onstanding is called a suspension. Water in a fast-flowing stream forms a suspension bypicking up rocks and soil that temporarily stay suspended in the moving water, but the Materials - settle out in layers on the stream bed, as did the beans andflour, when the water’s speed is reduced.

Layering